In the field, applications are known that try to automatically measure the emotional state of a user. This can for example be of interest to improve human-computer interaction. Examples of such products are ‘Journey to wild divine’ of the ‘Wild Divine’ company, and ‘FREEZE-FRAMER’®, of the company HeartMath. Both products measure e state of relaxation of the user.
There are different ways to measure particular emotions in an automated way. For example, it is known that changes in arousal/excitement/relaxation (relaxation being the opposite of arousal/excitement) affect the ANS (autonomous nervous system), which in turn alters the psychological/emotional state of a subject. This may be expressed in various physiological parameters, such as for example heart rate, blood pressure, respiration rate and GSR (galvanic skin response). Measuring techniques include measuring the tension of the muscles, recording the (ir)regularity of the heart rate and measuring the conductance of the skin. The latter is also known as GSR (galvanic skin response) or SCR (skin conductance response).
A GSR (or SCR) signal is a continuous signal that can be derived from the skin by a GSR sensor that measures the electrical resistance of the skin. In a known method that uses GSR the GSR signal is averaged over a certain time period such that noise is reduced and an estimation of the relative level of arousal over that time period is obtained. Another method detects peaks in the recorded GSR signal within a certain time period. A disadvantage of these methods is that they need an inconvenient period of calibration in advance to obtain baseline measurements that are used as reference values. Only after obtaining the baseline measurements an estimation of the level of arousal can be measured.